Area measuring by light



June 9, 1931. G..w. o. MARTIN ,3

AREA MEASURING BY LIGHT Filed-May 25, 1928 I 3 Sheets-Sheet l I7? 12 ez-rloz I H al' liz'zza y June 9, 1931. G. w. o. MARTIN AREA MEASURING .BY LIGHT Filed May 23, 1928 '3 Sheets-Sheet 2 fignt l I [Z'Zfo r77 6y G. w. o. MARTIN 1,809,346

AREA MEASURING BY LIGHT June 9, 1931.

3 Sheets-Sheet 5 Filed May 23. 1928 aff0i"776y Patented June 9 1931 UNITED: s'rA'rss PATENT OFFICE aims w. o. mrm, or imw'ro'n meminms, mssacnusn'r'rs, assrcnon. 'ro manmennemnnnmo comm, or EAST ros'ron, msacn'usn'r'rs, a conrom'rron OF MASSACHUSETTS ms. MEASURING 3! near My present invention relates to measuring devices, and'more particularly to an improved area measuring device for measu r.

.. m the superficial area of sheet material.

6 n the manufacture of leather, the measurcment of the area of the finished hide or skinis of great importance as the returns from the sale of such hides depends ordinarily on the area thereof. Numerous means 10 have been devised for'the purpose of accurately measuring the superficialarea of hides or skins, none of which, however, are so a curat'e as to leave no doubt in the mind of t producer that he is not selling more area he is gettin paid for. All of such prior devices haveamen improved from time to time but even at the present, none of them are reallyaccurate. y

In my dpresent invention, I have devised an improve apparatus for accurately measuring the superficial area of hides or skins or other sheet materials and have adopted an entirely new principle in my invention. I have, substituted for the heretofore mechanical measuring means, a combined light and electrical devlce which depends for its operation on the amount of intensit of light from a given area for controlling tile operation of an electrical indicating instrument, which electrical indicating instrument may be of any size or character desired and may be graduated to any degree of fineness desired, whereby the resulting measurements may be made as accurate as are considered necessar In carrying out my invention, I have ma e use of the well-known properties of the selenium'cell or photo electric cell, all having its conductivity altered by varying the in- .tensity or amount of light impinging thereon.

My preferred form of invention is illustrated in the fixed form of apparatus in which may be employed two methods of operation, called respectively, the two cell method and the flicker method. In the two cell method, Iemploy preferably a pair of .EilOtO electric cells havmg, as near as may identical, electrical characteristics, and in which"one of, the cells is continually exposed to constant illumination, while the light isv varied other cell is exposed to a fluctuatin illumination caused by insertin between t e source of light and the photo e ectric cell the hide or'skin whose area is to be measured' This method provides a very sensitive diflferential method for determining when two surfaces areequally illuminated and therefore enables a close measuring of the superficial area of a hide or skin.

In. the second method, known as the flicker method, a single hoto electrical cell is employed which is su jected to exposure by two. sources of light, the two sources of light ordinarily. being equal in intensity. By means of an appropriate shutter, the 'li ht from the 05 two sources is alternately cut 0 and turned on and the intensity of one of the sources of b the interposition of the hide or to e measured between such source and the photo electric cell. This also provides a differential scheme for accurately measuringxzhe superficial area of a hide or skin or 0t r sheetmaterial.

The object of my invention, therefore, is an im roved area measuring machine.

In fie accompanying drawin s illustrating the preferred embodiment o my invention Fig. 1 is a sectional side elevation of my device, taken on the line 11 of Fig. 2;-

Fig. 2 is a plan view taken on the line 22 of Fig. 1;

Fig. 3 is a side elevation taken on the line 3-3 of Fig. 1;

Fi 4 is a perspective view of therotatas in s utter;

ig. 5 is a perspective view of the outer casing of the photo electric cell showing the driving mechanism for a rotating shutter associated therewith;

Fig. 6 is a circuit diagram of one of the methods employed, and

Fig. 7 is a circuit diagram of the other method employed. v

Referring to the drawings, 10 designates 'a 95 rectangular case of any suitable material,

.provided with a transverse partition 11 tom of the casing is a plate 14, having attached centrally thereto and extending downwardly therefrom a lens box con taining a lens 16. Secured to the top of the plate 14 is a guide 17, in which works a Sllding shutter 18 to control the amount of exposure of the lens 16, such shutter 18 being operable from the outside of the casing 10. At various'points on the height of the casing 10 are arranged bars 19, on which may rest screens 20, the side walls of the casing 10 being perforated, as indicated at 21, to allow such screens 20 to be 0 erated from without the casing 10. Above t e screens 20 and parallel thereto, are arranged any desired number of sheets 22 of opa ue or'translu cent material, such as glass, 1; esesheets/being adjustably contained in slotted brackets 23 secured to the walls of the casing 10. Above the uppermost sheet 22 and in the casing 10 is secured plate 24, having secured to its under face a bank of preferably incandescent lamps 25, and the number "of lamps may be any desired, depending on the slze of the lamps and the intensity of the light it is desired to have emanate therefrom. For safety sake, the space surrounding the lamsps is lined with insulating material 26. ecured to the bottom of the casing 10 in alinement with the lens 16 in the lens box 15 is a standard or base 27 carrying at its upper face an adjustably mounted mirror or reflector 28, such mirror or reflector normally lying at an angle to the horizontal. A ort1on of the light emanating from the ban of lamps is projected downwardly and a cer-.

tain proportion thereof follows the direction of the arrows indicated in Fig. 1 for example, and passes through the lens 16 and lmfpinges on the mirror or reflector 28, which re ects it to the left, as shown in Fig. 1, and through a perforation or orifice in a member 29 forming part of the photo electric cell, such orifice being indicated diagrammatically in Fig. 7 by the reference numeral 30, and the photo electric cell being indicated diagrammatically by the reference numeral 31 in Fig. 7. A portion of the light emanating from the bank of lamps 25 passes horizontally through a perforation 32 in thepartition wall 11 and impinges on and is reflected by an adjustably mounted mirror 3'3 downwardly as indicated by the arrows in Fig. 1, where it impinges on and is reflected by an adjustably mounted mirror 34 located at the bottom of the casing 10 and in the direction of the arrow shown, passing through an orifice or perforation 35 in the partition wall 11, and thence passes through a perforation -or orifice in the member 29, as indicated diagrammatically in Fig. 7 by the reference numeral 36. l

The photo electric cell- 31 is. thus subjected to the light from the bank of lamps 25 direct- 7 ly and to the light from the bank of lamps 25 indirectly, and if the light from these sources passing through the perforations or*orifices 30 and 36, are equal in intensity, there will be no eflect produced in the photo electric cell 31. If, however, a sheet of leather or other sheet material is placed on one of the screens 20, it is obvious that a portion of the light emanatin from the bank of lamps 25 and passing ownwardl will be intercepted so that the amount of hght passing throu h the lens 16 and entering the orifice 30 will e less than the amount of ii ht passing from the bank of lamps 25 and ollowing the path defined by the mirrors 33 and 34 and entering the erforation or orifice 36. Under these con ltions, a certain effect will be produced in a photo electric cell 31. Surrounding the end of the member 29, is a shutter 37, which is connected to the end of a shaft 38? rotated by means of a belt 39 from any suitable source of power, as an electric motor 40. By

'means of the shutter 37 the light is alternately cut off and turned on at the orifices 30 and 36.

Referrin now to Fig. 7 ,which illustrates a preferred orm of circuit arrangement and indicating'means utlhzed in connection with the structures above described, there is indi cated, as above pointed out, the orifices 30 and 36 and the photo electric cell 31. The photo electric'cell 31 is connected to a vacuum.t ube 41 and the vacuum tube 41 is connected in any well known manner through the amplifying circuits indicated nerally by the reference character 42. C o nnected to the amplifying circuit 42 is a transformer 43 where the current in the amplifying cir-- cuit 42 is changed to an alternating voltage and the secondary of this transformer 43 is connected to a commutator 44 rotated by suitable means in synchronism or in phase with the rotating shutter 37. Connected to the commutator 44 by electrical indicating mstrument 47 such as a galvanometer.

In operation, a source of current is turned into the bank of lamps 25 and the mirrors 33 and 34 adjusted until a beam of light from such bank of lamps 25 passes into the orifice 36. Also the shutter 18 is adjusted with respect to the lens 16, until the light reflected by the mirror 28 not only passes through the orifice 30, but is also of equal intensity to; the light passing through the orifice 36.-

Under these conditions, therefore, no indication will appear inthe indicating instrument 47. Power is turned into the motor to rotate the shutter 37 and thus the light from the photo-electric cell 31 is alternately cut off at the orifices 30' and 36. As long as the intensity of the light through the two OElfiCGS is equal, no effect will be produced in t e sheet of leather or other sheet material 48 is placed on one or the other of the screens 20,

photo electric cell 31. If, however, a

leads 45 and 46 is an mam then acertain amount of light thatordinarily passes downward throu h the lens 16 will be blocked and on the contlnuous rotation of the shutter 37, a light of varying intensity will be alternately passed onto and oil the photo electrie'c'ell 31. The intensity of the two sources of -lightconsidering the ,two sources as being present at the orifices 30 and 36-wiLl be unequal and the effect ofthi-s varithe grid of the vacuum tube 41.

42 above referred toand a alternating cur-iation of intensity is to generate, by means of the photoelectric cell, a varying potential on J This potential is employed in the amplifying circuit rent is-produced in the plate circuit of the last stage-of amplification, .where such alternating current is changed to an alternating voltage in the transformer 42, from which it is fed to a commutator 44, rotated inphase with the cap or shutter'37. By means of the commutator 44 there is produced a pulsat ing direct current, the average value of which 7 depends on the ratio of the intensity, of the light passing through the orifices 30 and 36,

current will depend on the relative values of the intensity of the light passing through the orifices 30 and 36. ,The pulsating cur- 3 rent passing through the indicating instruis exposed to the light passing through the single relay 55, and a bell or-other indicating lens 16, while the photo electrid cell 51 is exposed to the light reflected from the mirror 34. The illumination of the photo electricv cell. 50, therefore, will depend,other things being constant, on the area of the leather to be measured and placed on one or the other of the screens 20. Connected in circuit-.withthr':v

photo electric cells 50 and 51 isa vacuum tube 52, a milliammeter 53, a double relay 54, a

device 56 Assuming that the cells 50 and 51 have identical characteristics and are connected, as shown in Fig. 6, and with the photo electric cell being illuminated by. the light from the bank of lamps 25 directly and the photo electric cell 51 being illuminated by the bank of lamps 25 indirectly, then if a sheet of leather or other flexible material 48 is placed on one or the other of the screens 20,

the amount of light normally passing to the photo electric cell 50 is reduced. This reduction in the amount of light will increase the resistance of the photo electric cell 50 and will cause the grid of the vacuum tube 52 to and also the direction of this pulsating direct become o sitive The change in the condition of t e vacuum tube'52 will increasethe current through the milliammeter 53 and the area of the piece of leather 48 may be measured directly, assuming the milliammeter to be properly calibrated. Also, the circuit through the milliammeter 53 being increased,

the contact of the double relay 54 will-be held fast and current will be held through the single relay coil-55, which, inturn, will hold its armature inopen position and keep the circuit for the electric bell 56 open. If. the sheet of leather 48 is now withdrawn from the screen 20, the amount of light passing to the photo electric cell 50 will be'increasedvand a point will be reached where the resistance.

in the cell 50 is about equal to that of the cell ,51, This increase in the intensity of the light will cause ,the grid of the vacuum tube 52 j to become negative, thereby diminishing'the circuit through the milliammeter 53 and allowing the double relay 54 to let go its contact. This in turn de-energizes the relay 55 and the armature thereof wilLclose circuit for the electric bell 56, thereby causing said bell to ring.

This method as outlined above, and as diagrammatically illustrated in Fig. 6, is an extremely sensitive differential method for determining when two surfaces are equally illuminated and, therefore, may be utilized to accuratelymeasure the superficial area of any material by means of which the light from one of the surfaces is reduced. This method, however, has the disadvantage that i the two cells 50 and 51 may not have identi cal characteristics.

Having thus described my invention, what i I claim as new is:

An improved dev ce for measurmg the superficial area of hides or SklIlS comprising a photo electric cell, amplifying and indicating devices associated therewith, a light, means for dividing said source of light into two' beams which lmpinge on the photo electric cell at two separate and distinct points,

means for alternately cutting off the beams of 1 light from the .photo electric cell and means associated with said photo electric cell for indicating variations in'the intensity of the lights in one of said beams due to the interposition of a hide or skin therein.

In testimony'whereof, I have signed my name to this specification.

GILES wxo. MARTIN. 

